Table 7.
Risk-of-bias assessment
| Studies | Selection | Comparability | Outcome | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Representativeness of the exposed cohort | Selection of the non exposed cohort |
Ascertainment of exposure |
Demonstration that outcome of interest was not present at start of study | Comparability of cohorts on the basis of the design or analysis | Assessment of outcome | Was follow-up long enough for outcomes to occur |
Adequacy of follow up of cohorts |
|||
| Chen et al.24 | ★ | - | - | ★ | - | ★ | - | - | ||
| Fäh and Schätzle25 | ★ | ★ | - | ★ | - | ★ | - | - | ||
| Gurdan and Szalma26 | ★ | - | ★ | ★ | - | ★ | ★ | - | ||
| Hourfar et al.27 | ★ | - | ★ | ★ | - | ★ | - | - | ||
| Jia et al.28 | ★ | - | ★ | ★ | - | ★ | - | - | ||
| Jung et al.29 | ★ | - | ★ | ★ | - | ★ | ★ | - | ||
| Takaki et al.30 | ★ | - | ★ | ★ | - | ★ | - | - | ||
| Ziebura et al.31 | ★ | - | ★ | ★ | - | ★ | ★ | - | ||
The Newcastle-Ottawa Scale consists of 8 multiple-choice questions that address subject selection (4 questions), comparability (1 question), and outcome assessment (3 questions). High-quality responses would be awarded up to 9 points (the comparability question earns up to 2 points).